284 research outputs found
Some Thoughts About Appealing Directions for the Future of Fuzzy Theory and Technologies Along the Path Traced by Lotfi Zadeh
The quoted text is an interesting instance of a fuzzy object: it is currently known in slightly diversified forms, each rather different from the quoted one, which corresponds to the first known appearance in English of this adage
Grover's algorithm on a Feynman computer
We present an implementation of Grover's algorithm in the framework of
Feynman's cursor model of a quantum computer. The cursor degrees of freedom act
as a quantum clocking mechanism, and allow Grover's algorithm to be performed
using a single, time-independent Hamiltonian. We examine issues of locality and
resource usage in implementing such a Hamiltonian. In the familiar language of
Heisenberg spin-spin coupling, the clocking mechanism appears as an excitation
of a basically linear chain of spins, with occasional controlled jumps that
allow for motion on a planar graph: in this sense our model implements the idea
of "timing" a quantum algorithm using a continuous-time random walk. In this
context we examine some consequences of the entanglement between the states of
the input/output register and the states of the quantum clock
Tight Bounds for SVM Classification Error
We find very tight bounds on the accuracy of a Support Vector Machine classification error within the Algorithmic Inference framework. The framework is specially suitable for this kind of classifier since (i) we know the number of support vectors really employed, as an ancillary output of the learning procedure, and (ii) we can appreciate confidence intervals of misclassifying probability exactly in function of the cardinality of these vectors. As a result we obtain confidence intervals that are up to an order narrower than those supplied in the literature, having a slight different meaning due to the different approach they come from, but the same operational function. We numerically check the covering of these intervals
Speed and entropy of an interacting continuous time quantum walk
We present some dynamic and entropic considerations about the evolution of a
continuous time quantum walk implementing the clock of an autonomous machine.
On a simple model, we study in quite explicit terms the Lindblad evolution of
the clocked subsystem, relating the evolution of its entropy to the spreading
of the wave packet of the clock. We explore possible ways of reducing the
generation of entropy in the clocked subsystem, as it amounts to a deficit in
the probability of finding the target state of the computation. We are thus
lead to examine the benefits of abandoning some classical prejudice about how a
clocking mechanism should operate.Comment: 25 pages, 14 figure
The digital whomanities project. Best practices for digital pedagogy in the pandemic era
This paper aims to enter the ongoing debate about the critical issues of digital pedagogy through the presentation of Digital WHOmanities, a series of online conferences and workshops held at the University of Bologna. Distance learning has become one of the most discussed topics in educational institutions during the spread of Covid-19, revealing a discrepancy between the rapid development of technology and the ability of learning environments to adapt to this turn. In view of this ongoing debate, Digital WHOmanities tried to define the complex and multifaceted figure of the digital humanist and to provide a methodological framework that could foster further online academic initiatives. Specifically, the accurate organization of timing and contents and the adoption of synchronous and asynchronous approaches have highlighted the effectiveness of flexible digital didactics
A systematic review of the literature on the role of tracheostomy in COVID-19 patients
– The Coronavirus Disease 2019 (COVID-19) is a viral infection caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which emerged in East Asia and spread around the world from December 2019. The most severe stage of COVID-19 pathology is characterized by respiratory distress requiring intubation. In specific cases, tracheostomy is indicated to ensure the safety of the procedure. The aim of our study was to analyze the scientific literature identifying the indications for tracheostomy and safety precautions to reduce contamination. We analyzed the literature from February 2003 to April 2020, including papers on pandemics of other coronaviruses, such As Severe Acute Respiratory Syndrome Coronavirus 1 and Middle East Respiratory Syndrome Coronavirus, to obtain a variety of relevant information. We focused on indications for tracheostomy in patients affected by COVID-19 or related viruses and the measures adopted to perform a safe procedure. We included 35 papers, of which 24 (68.57%) discussed guidelines for tracheostomy indications. All 35 studies discussed the procedures for performing tracheostomy safely. Data obtained indicated that the authors generally agreed on safety measures but expressed different opinions about indications. Therefore, we provided guidelines addressing safety recommendations. After the pandemic has been resolved, we plan to conduct an international retrospective study to identify the criteria for tracheostomy indications
Quantum Annealing and Analog Quantum Computation
We review here the recent success in quantum annealing, i.e., optimization of
the cost or energy functions of complex systems utilizing quantum fluctuations.
The concept is introduced in successive steps through the studies of mapping of
such computationally hard problems to the classical spin glass problems. The
quantum spin glass problems arise with the introduction of quantum
fluctuations, and the annealing behavior of the systems as these fluctuations
are reduced slowly to zero. This provides a general framework for realizing
analog quantum computation.Comment: 22 pages, 7 figs (color online); new References Added. Reviews of
Modern Physics (in press
The power of quantum systems on a line
We study the computational strength of quantum particles (each of finite
dimensionality) arranged on a line. First, we prove that it is possible to
perform universal adiabatic quantum computation using a one-dimensional quantum
system (with 9 states per particle). This might have practical implications for
experimentalists interested in constructing an adiabatic quantum computer.
Building on the same construction, but with some additional technical effort
and 12 states per particle, we show that the problem of approximating the
ground state energy of a system composed of a line of quantum particles is
QMA-complete; QMA is a quantum analogue of NP. This is in striking contrast to
the fact that the analogous classical problem, namely, one-dimensional
MAX-2-SAT with nearest neighbor constraints, is in P. The proof of the
QMA-completeness result requires an additional idea beyond the usual techniques
in the area: Not all illegal configurations can be ruled out by local checks,
so instead we rule out such illegal configurations because they would, in the
future, evolve into a state which can be seen locally to be illegal. Our
construction implies (assuming the quantum Church-Turing thesis and that
quantum computers cannot efficiently solve QMA-complete problems) that there
are one-dimensional systems which take an exponential time to relax to their
ground states at any temperature, making them candidates for being
one-dimensional spin glasses.Comment: 21 pages. v2 has numerous corrections and clarifications, and most
importantly a new author, merged from arXiv:0705.4067. v3 is the published
version, with additional clarifications, publisher's version available at
http://www.springerlink.co
Quantum Simulations of Classical Annealing Processes
We describe a quantum algorithm that solves combinatorial optimization
problems by quantum simulation of a classical simulated annealing process. Our
algorithm exploits quantum walks and the quantum Zeno effect induced by
evolution randomization. It requires order steps to find an
optimal solution with bounded error probability, where is the minimum
spectral gap of the stochastic matrices used in the classical annealing
process. This is a quadratic improvement over the order steps
required by the latter.Comment: 4 pages - 1 figure. This work differs from arXiv:0712.1008 in that
the quantum Zeno effect is implemented via randomization in the evolutio
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